It was supposed to be a wonder drug, the great hope for
battling AIDS.

Now, AIDS researchers have begun warning South African volunteers who took Merck V520-023 that the experimental vaccine is not only ineffective, but that it also may have increased their susceptibility to contracting HIV, the virus that causes AIDS.

An undisclosed number of Seattle volunteers received the same vaccine as a part of a separate clinical trial called "STEP." The Seattle-based HIV Vaccine Trials Network (HVTN) co-sponsored both the STEP clinical trials and the South Africa trial, known as the "Phambili" study. The US STEP trials has 3,000 volunteers.

The HVTN and Merck, the pharmaceutical company that developed the vaccine, have not yet decided when they will inform study participants elsewhere whether they had taken the vaccine or a placebo, citing concerns that the study's results might be compromised if they were to "un-blind" participants at this time.

The warnings in South Africa follow September's announcement that the clinical trials for V520-023 were being halted.

Researchers said preliminary studies showed the substance, which was given to uninfected South African volunteers at high risk for acquiring HIV, was proving to be an ineffective vaccine. Among the 801 volunteers who received at least two doses of the vaccine, 19 contracted HIV, compared with 11 of those given placebos, The Washington Post reports.

Though the vaccine could not have caused the infection, researchers say it could have caused changes to the body's immune system that would have made it easier for the virus to take hold during a later exposure. Unlike traditional vaccines that coaxed the body to create antibodies to protect against a target virus, V520-023 was designed to coach immune system cells, through exposure to something similar to the common cold virus, to attack the virus that causes AIDS.

"This is my worst nightmare," Glenda Gray, the lead South Africa investigator for the vaccine study, told The Washington Post. "I haven't slept for days. I have a headache. I'm ready to resign from trials for the rest of my life."

In Seattle, Sarah Alexander, Associate Director for Communications and External Relations for the HVTN, said test sites had received phone calls from trial participants concerned about the news from
South Africa.

However, she added that communication has been going in "both directions," and that those sites are also currently in the process of calling "every one" of the volunteers to keep them informed about the study.

"Every study gets un-blinded at some point," said Alexander. "The plan for how to un-blind this study isn't in place yet. That's one of the main things that we'll be discussing at a Nov. 7 meeting."

Alexander's comments helped contextualize a statement issued by Mark Feinberg, vice president for medical affairs and policy for Merck. Feinberg said that the ethics oversight board in the United States, which monitored the trial everywhere but in South Africa, had not yet decided whether to tell participants if they received the placebo of the vaccine.

However, Alexander explained that this was not a matter of HVTN or other researchers misleading study participants, but attempting to ensure the research will not
be compromised.

"If someone walks into one of the sites and says, 'I don't like this indecision, I want to know,' we un-blind them," Alexander added. "First we explain to them why we would like them to consider staying blinded, but then if they say, 'No, those reasons don't matter to me,' then we un-blind them."

Alexander explained that the Nov. 7 meeting in Seattle will address a plan for un-blinding participants. The HVTN holds two large scientific meetings a year that brings together scientists, investigators, clinic coordinators, community educators, community advisory board members, and representatives from the National Institute of Allergy and Infectious Diseases, the federal organization that funds HVTN, to discuss progress in the battle to fight HIV and AIDS. August's AIDS Vaccine 2007 Conference drew nearly 1,000 health experts to Seattle.

"They are not open meetings generally, but this year, at the Nov. 7 meeting, the morning session will be open because it is the discussion of the study's results," said Alexander. "Whether we continue in a blinded fashion with the study or have participants be un-blinded, there are scientific advantages either way. All of that will be a part of a discussion, and the reason that it's happening Nov. 7th is that we do have a significant group of community people who are part of the network that come to that, and these are decisions that should involve the community. They are not just for the scientists to determine."

The STEP clinical trial began enrolling about 3,000 volunteers in 2004 for study sites in Australia, Brazil, Canada, the Dominican Republic, Haiti, Jamaica, Peru, Puerto Rico and the United States.

The South African trials were tested in the separate "Phambili" study administered by the HVTN and the South African AIDS Vaccine Initiative.

Though the South African trial was smaller in scope, it tested the same Merck candidate HIV vaccine being used in the STEP trials. Beginning in February of 2007, scientists started recruiting men and women of different races, sexual orientations, and economic backgrounds in four provinces, Gauteng, North West, Western Cape and KwaZulu-Natal, for the study. At least 5.5 million South Africans have AIDS, according to the UNAIDS 2006 Report on the global AIDS epidemic.

Merck's new hope for an effective AIDS drug lies in Isentress, an HIV suppressor that "has performed well in clinical trials and has been hailed as the most important new AIDS drug in a decade," The New York Times reports.

On Oct. 15, the Food and Drug Administration granted Merck approval for Isentress, also known by its generic name,
"Raltegravir."

More than 80 percent of the volunteers who took Isentress in clinical trials saw the virus load in their blood drop to barely detectable levels, according to the Times-something the vaccine V520-023 has also failed to do in preliminary studies.